Oenothera elata is our most common upper elevation Evening Primrose [in the Gila Wilderness, New Mexico], just as Oenothera caespitosa is our most common lower elevation one. Oenothera elata is usually single stemmed and stands strongly erect. The petals are yellow turning orange with age. The stem is reddish. The leaves are lanceolate and sessile. Oenothera elata is commonly seen at the roadside at upper elevations. The seeds are irregularly shaped and stacked in the capsules. The capsules when mature are woody, brown and have four chambers each with two rows of small angled seeds.

Heil et al. 2013, Allred and Ivey 2012, Martin and Hutchins 1980

Duration: Perennial Nativity: Native Lifeform: Forb/Herb General: Biennial to short-lived perennial herb, 30-250 cm tall, from a stout woody taproot; stems solitary or several, erect, branching above the middle, and covered with short appressed hairs. Leaves: Alternate along the stems, and also in a basal rosette which sometimes persists until the plant flowers; blades oblanceolate to narrowly lanceolate, 4-25 cm long and 1-3 cm wide, the edges lined with blunt teeth or almost smooth (entire); basal leaves much larger, with sinuate-dentate edges. Flowers: Showy and yellow, arranged in dense, erect spikes at branch tips; hypanthium (floral tube located below the sepals and petals) cylindrical, 2-5 cm long; sepals 4 per flower, 3-5 cm long, pointed downward (reflexed) in full flower; petals 4 per flower, 25-65 mm long, yellow and fading to orange-yellow. Fruits: Capsules narrowly lanceoloid and bluntly 4-angled, 2-7 cm long and 4-7 mm wide; splitting open along 4 longitudinal suture lines to release many reticulate-pitted seeds, 1-2 mm long. Ecology: Found along streams, in meadows, and in disturbed sites, from 3,500-10,000 ft (1067-3048 m); flowers June-September. Distribution: s WA to CA, east to OK and TX; south to n MEX. Notes: A tall, showy, erect yellow-flowered evening primrose, with leaves that are often lined with minute teeth around the edges but are never deeply lobed as in many other Oenothera spp. Oe. rhombipetala is similar but has rhomboid-shaped petals which are widest at the middle, while this species has petals which are widest near the tip. Oe. villosa and Oe. biennis are also tall with large yellow flowers; distinguish among them by looking at the flowers. Oe. elata has flowers with the style exserted 2-4 mm beyond the floral tube, the stigma elevated above the anthers at full flower, and petals 25-65 mm long. Oe. vilolosa and Oe. biennis both have a style exserted much farther beyond the floral tube, up to 1.5 cm; the stigma surrounded by or below the anthers at full flower; and usually smaller petals, 10-25 mm long, though they may be longer. Oe. elata material from the southwest belongs to subsp. hirsutissima. Ethnobotany: Used as a cold remedy and in a poultice for swellings; also used as a ceremonial emetic. Etymology: Oenothera comes from the Greek oinos, wine, and therao, to seek or imbibe, alluding to the fact that the root of Oenothera biennis was used to flavor wine; elata means tall in Latin; hirsutissima means very hairy. Synonyms: Oenothera hookeri subsp. hirsutissima Editor: AHazelton 2017